FixVault
Home › Saturn › 2003 › L200 Standard › Repair and Diagnosis › Engine Performance › System › Engine Controls - Self-Diagnostics › Diagnostic Tests › DTC P0300: Engine Misfire Detected › Diagnostic Procedures

Diagnostic Procedures

  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
    2. NOTE: You must perform the CKP system variation learn procedure before proceeding with this diagnostic test. Refer to CRANKSHAFT POSITION VARIATION LEARN PROCEDURE .
  2. Start and allow engine to idle or operate within the conditions listed in the Freeze Frame/Failure Records. Monitor all of the Misfire counters with the scan tool. Are any of the Misfire Current counters incrementing? If yes, go to next step. If no, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 2.2L SATURN "L" SERIES article.
  3. Are any other DTCs set? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  4. Can any abnormal engine noise be heard? If yes, diagnose for an engine mechanical problem. If no, go to next step.
  5. Inspect vacuum hoses and seals for splits, restrictions, and improper connections. Inspect crankcase ventilation system for vacuum leaks, PCM grounds for corrosion and loose connections, exhaust system for restrictions, or fuel for contamination. Did you find and correct the condition? If yes, go to step  19. If no, go to next step.
  6. Turn ignition off. Remove the fuel pump relay. Remove the ignition coil housing assembly, keeping the IC module assembly connected to the harness connector. Not grounding the IC module housing may cause an erratic spark. Connect a jumper wire between the top of the IC module and a good ground. Install the Ignition System Diagnosis Harness (J 36012-A). Install Spark Tester (J 26792) on the No. 1 spark plug jumper wire. Ground the No. 4 spark plug jumper wire. The No. 4 wire is the companion to No. 1. Crank engine with the remaining spark plug wires connected. Repeat steps by installing the spark tester on No. 4 and grounding No. 1. Do the same for the No. 2 and No. 3 spark plugs. Ensure the companion wire is grounded. Does the spark tester spark on all cylinders? If yes, go to next step. If no, diagnose Electronic Ignition (EI) System.
  7. Remove the spark plug from the cylinder that indicated a misfire. Inspect the spark plug. Does the spark plug appear to be okay? If yes, go to next step. If no, go to step  9.
  8. Exchange the suspected spark plug with another cylinder that is operating properly. Operate the vehicle under the same conditions that the misfire occurred. Did the misfire move with the spark plug? If yes, go to step  15. If no, go to step  12.
  9. Is the spark plug oil or coolant fouled? If yes, diagnose for an engine mechanical problem. If no, go to next step.
  10. Is the spark plug gas fouled? If yes, go to step  13. If no, go to next step.
  11. Did the spark plug show any signs of being cracked, worn, or improperly gapped? If yes, go to step  14. If no, go to next step.
  12. Perform the fuel injector coil test. See FUEL INJECTOR COIL TEST in SYSTEM & COMPONENT TESTING - 2.2L SATURN "L" SERIES article. Did you find and correct the condition? If yes, go to step  19. If no, diagnose for an engine mechanical problem.
  13. Perform the fuel system diagnosis. Did you find and correct the condition? If yes, go to step  16. If no, diagnose for an engine mechanical problem.
  14. Replace or gap the spark plug. After repairs, go to step  16.
  15. Replace faulty spark plug. After replacement, go to next step.
  16. Was the customer's concern regarding the MIL flashing? If yes, go to next step. If no, go to step  18.
  17. Operate engine at 2500 RPM for 4 minutes. Operate the vehicle within the Conditions for Running the DTC P0420. Refer to DTC P0420: CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1) . Does the DTC run and pass? If yes, go to next step. If no, go to DTC P0420: CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1) .
  18. Clear DTCs with scan tool. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  19. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
About FixVault